The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a functional block diagram of a wireless communications system is presented. A home network 102 receives packets from and sends packets to a distributed communications system 104, such as the Internet. A wireless terminal 106 wirelessly connects to the home network 102. For example, the wireless terminal 106 may be a mobile phone, and the home network 102 may be the cellular network of a mobile phone operator. The wireless terminal 106 is configured to work with the home network 102, and may be unable connect to the networks of other carriers. In various implementations, the wireless terminal 106 may be able to view content from the Internet 104 via the home network 102. The home network 102 may also interconnect with the networks of other service providers.
Referring now to FIG. 2, a functional block diagram of a wireless communications system offering mobility is presented. The home network 102 is connected to one or more visited networks 110. For example only, FIG. 2 depicts three visited networks 110-1, 110-2 and 110-3. In various implementations, the visited networks 110 may be the networks of other service providers, including service providers in other countries.
A mobile wireless terminal 120 includes mobility features that allow it to communicate with the visited networks 110. For example, in FIG. 2, the mobile wireless terminal 120 has established a wireless connection to the visited network 110-1. The mobile wireless terminal 120 includes the code and data used to communicate with the home network 102 via the visited network 110-1. In this way, the mobile wireless terminal 120 can interface with the home network 102 even when connected to one of the visited networks 110.
Referring now to FIG. 3, a functional block diagram depicts a wireless communications system that provides proxy mobility to the wireless terminal 106. A home network 150 communicates with visited networks 160-1, 160-2, and 160-3. The visited networks 160 provide transparent mobility to wireless terminals, such as the wireless terminal 106, that have not been updated to include mobility functionality.
When the wireless terminal 106 attempts to establish a link with the visited network 160-1, the visited network 160-1 determines the network to which the wireless terminal 106 belongs. In this case, the visited network 160-1 determines that the home network 150 is the appropriate network. The visited network 160-1 then forwards packets from the wireless terminal 106 to the home network 150 and passes packets from the home network 150 to the wireless terminal 106. The wireless terminal 106 is therefore oblivious to the fact that it is connected to the visited network 160-1 instead of to the home network 150.
Referring now to FIG. 4, a more detailed functional block diagram of an implementation of proxy mobility is presented. Proxy mobility may also be referred to as network-based mobility because the network provides mobility to a terminal that does not have built-in mobility. In an Internet Protocol (IP) network, proxy mobility may be referred to as proxy mobile IP (PMIP). The home network 150 includes a home agent 202. The home agent 202 establishes the logical location of the wireless terminal 106. Packets destined for the wireless terminal 106 are first sent to the home agent 202, while packets from the wireless terminal 106 will appear to originate from the home agent 202.
The wireless terminal 106 may establish a connection to an attachment point 206-1 within the visited network 160-1. In various implementations, additional attachment points, such as attachment points 206-2 and 206-3, may be present. The attachment points 206 may communicate with other networks, including the home network 150, via a gateway 210.
Referring now to FIG. 5, a timeline of steps performed when the wireless terminal 106 connects to the visited network 160-1 is presented. First, the wireless terminal 106 performs access and authentication with the attachment point 206-1. This may include communicating with an Access, Authentication, and Accounting (AAA) server. Upon authentication, the wireless terminal 106 attempts to attach to the attachment point 206-1.
The AAA server may use an identifier of the wireless terminal 106, such as a network address identifier, that uniquely identifies the wireless terminal 106. The attachment request requests an IP address from the attachment point 206-1. The attachment point 206-1 determines the appropriate home agent for the wireless terminal 106. This information may be supplied by the wireless terminal 106 and/or may be supplied by the source of the authentication information.
The attachment point 206-1 then sends a binding update message to the home agent 202. The home agent 202 allocates an IP address, IP1, to the wireless terminal 106. The address IP1 is used for communications with the wireless terminal 106. When the wireless terminal 106 sends a packet, that packet will appear to originate from the home agent 202 with a source address of IP1. In addition, packets destined for the wireless terminal 106 are sent to the home agent 202 with a destination of IP1.
The home agent 202 sends a binding acknowledgement message including IP1 to the attachment point 206-1. A tunnel is then set up between the attachment point 206-1 and the home agent 202 for transmission of packets to and from the wireless terminal 106. The attachment point 206-1 then assigns IP1 to the wireless terminal 106. In this process, the wireless terminal 106 has requested an IP address from the attachment point 206-1 and has received one. The wireless terminal 106 is not, and does not need to be, aware that it is connected to the visited network 160.
Referring now to FIGS. 6 and 7, a packet being sent by the wireless terminal 106 and a packet being sent to the wireless terminal 106, respectively, are graphically depicted. Referring now to FIG. 6, a packet 242 is transmitted to the wireless terminal 106. The source of the packet 242 is IP1, the IP address assigned to the wireless terminal 106. The destination of the packet 242 is the IP address, denoted IPdest, to which the wireless terminal 106 is sending the packet 242. The packet 242 may also include a payload.
The packet 242 is received by the attachment point 206-1. The attachment point 206-1 tunnels the packet 242 to the home agent 202. The packet 242 is tunneled by encapsulating it within an encapsulating packet 244. The header and payload of the packet 242 is placed in the payload of the encapsulating packet 244. The encapsulating packet 242 has a source address of the attachment point 206-1, IPAP, and a destination address of the home agent 202, IPHA.
When the home agent 202 receives the encapsulating packet 244, the home agent 202 extracts the original packet 242 from the payload of the encapsulating packet 244. The packet 242 is then routed to the destination indicated by IP dest. For example only, this may be an address on the Internet 104.
Referring now to FIG. 7, a packet 252 is received by the home agent 202 for the wireless terminal 106. The packet 252 has a source address of the sender of the packet 252, designated IPsrc. The destination address of the packet 252 is the address assigned to the wireless terminal 106, IP1. The home agent 202 recognizes the destination address of IP1 and tunnels the packet 252 to the attachment point 206-1.
The packet 252 may be tunneled by encapsulating it within the payload of an encapsulating packet 254. The source address of the encapsulating packet 254 is the address of the home agent 202, IPHA. The destination of the encapsulating packet 254 is the address of the attachment point 206-1, IPAP. The attachment point 206-1 extracts the packet 252 from the payload of the encapsulating packet 254 and forwards the packet 252 to the wireless terminal 106.